France's president, Nicolas Sarkozy, will tonight confront the biggest challenge yet to his six-month tenure, when transport and utility workers begin open-ended strike action which could paralyse the country, deepening the sense of a "November of discontent".

Unions and the left yesterday accused Sarkozy of deliberately forcing workers onto the streets for a showdown over pensions reform in order to portray himself as a hard-man reformer who is prepared to stand his ground.

From 8pm tonight, transport, gas and electricity workers, and staff at the Paris Opera and Comédie Française, will down tools in protest at plans to end special pension benefits enjoyed by certain public sector workers. Ending these special deals is key for Sarkozy if he is to retain his image as a tough reformer and push through more difficult changes in labour law and general pensions early next year.

The special deals - which date back to the end of the second world war or, in some cases, to the time of Louis XIV - allow certain workers, such as train drivers, to retire early on favourable packages because their jobs were historically seen as dangerous or strenuous.

A 24-hour strike over the issue last month was the country's biggest industrial action for more than a decade. But this week's strike is open-ended and can be renewed day by day.

The government fears the spread of a "contagion" which could see the strike prolonged to join up with other protest action planned for coming weeks. Next Tuesday, public sector workers, including teachers, civil servants, post and telecom workers will stop work for 24 hours in protest at Sarkozy's plans to cut jobs in the bloated state sector. On November 29, magistrates will take to the streets over cuts to the courts system. Already, students, largely on the hard left, have started blocking faculties in protest at university reforms voted in this summer.

Sarkozy, who has styled himself as the man who can solve France's economic problems, insisted yesterday: "The door will always be open for dialogue. But we will carry out these reforms because they have to be done." The employment minister, Xavier Bertrand, refused to hold last-minute talks between the government, unions and company bosses. He said the reform would go ahead and the "status quo" was "unthinkable".

Bernard Thibault, head of the Communist-leaning CGT union, criticised the government's stance, warning that it had deliberately forced the unions on to the street, stoking conflict, "to set an example". He said he was prepared for a long strike.

Sarkozy is counting on public opposition to the strike. A survey last month showed 77% of French people were in favour of reforming the special pension privileges, which are seen as unfair. Recent polls have shown limited support for the strike action.

Sarkozy, keen to contain the wider protest movements gathering pace, has recently been seen making concessions to other unhappy constituencies, such as Breton fishermen. When the fishermen protested over the price of diesel, they received a presidential visit, €30m (£21m) in aid and cuts to social charges. Protesting students have also been promised a generous aid package for housing. Such gifts have been seen as mixed messages. As Sarkozy marks six months in power, some of his reforms have already seen slight tweaks, postponement and watering down. The unions are now determined to stand their ground before further major reforms next year.

The Socialist MP Bruno Le Roux warned yesterday: "The government must not think that the anger in this country is limited to the railway workers or those on special pension deals. Today in our country, there is a general discontent."

Backstory

French governments have repeatedly run into trouble when trying to axe public sector retirement deals. In December 1995, an attempt by Jacques Chirac's first government, under Alain Juppé, prompted three weeks of strikes which paralysed public transport and disrupted schools and the postal service. Juppé eventually abandoned the pensions reform but it contributed to the defeat of the centre-right in 1997.

In 2003, when François Fillon, then work minister and now prime minister, launched his pensions reform, he left the special state pensions privileges untouched to avoid strikes. But attempts to reform restrictions on hiring and firing young workers triggered protests last spring which saw millions march on the street against Dominique de Villepin, the prime minister.